It is well known to use polypropylene fibres have been used as a secondary reinforcement additive to concrete. As well, work has been done with polypropylene fibres in shotcrete, asphalt and other composite materials. However the fibres used have been manufactured from virgin resin which adds cost to the concrete and overlooks the potential resource of used polypropylene material.
The agricultural community generates many thousands of metric tonnes of used polypropylene baler twine during the normal course of its activities. Polypropylene twine is used to bale hay and straw by farmers and ranchers. After its first instance of usage the used polypropylene twine is normally discarded and transported to landfills. This discarded polypropylene twine is problematic for landfill operators as it tends to wrap around crawler tractor undercarriages thereby causing premature wear and damage to exposed bearings and lubrication seals. Incineration of polypropylene is not a optimal alternative because of the production of noxious gases. Incineration of this material creates environmental air quality concerns.
Used polypropylene twine is usually contaminated with hay, straw, twine and fecal matter. It is difficult to process because it is collected in tangled piles and is of varying lengths. For these reasons. traditional methods of recycling polypropylene such as melt and re-extrude, are not effective. As well, the different sources of the polypropylene results in a wide variance in melt temperatures which further complicates prior art recycling methods.
In order to be recycled into fibres suitable for use as a reinforcing additive, the twine must be cleaned, skeined or bundled and cut to pre-determined and uniform lengths, and broken down into individual component fibres.
It would therefore be advantageous to have a method and apparatus for processing the used polypropylene twine into individual component fibres which are suitable for use as a secondary reinforcing material for concrete and other structural materials.